Need help on project - Charging under load?

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Hello Everyone…

I have a project I’m working on where I need to install a single security camera connected to a wireless network bridge. The camera will be mounted on a wall and the network bridge will be mounted around the corner about 15 feet pointed back at the access point.

The camera pulls 1.9 amps at 12 volts DC. The Network Bridge pulls 0.5 amps at 24 volts DC.

The property has a lot of blackouts for some reason. These tend to last anywhere from 1 hour up to 48 hours in some cases so this remote rig needs some sort of battery backup to keep it going during these blackout events.

Right now there is an 110AC outlet installed in a 12 X 12 junction box. One of the outlets has a 110 AC input to 24VDC @ 0.5 amps output wall wart that goes to a POE injector on the Bridge Radio. The other outlet has an 110AC to 12VDC @ 2.0 amps output that goes to the power input on the camera. There is a CAT5 between the camera and the POE injector network input.

I know enough to know I could wire two 12DVC batteries in series and get 24VDC out and that could power the Network Bridge Radio. I could just tap on to one of the two batteries for the 12VDC for the cameras power but not sure if that’s going to affect that one battery in a bad way. I guess the other option might be to use a buck converter on the 24VDC and step it down to 12 for the camera. The only reason I think that might be better is so both batteries are evenly sharing the entire load.

I have tested both of those scenarios and of course it works just fine with either way but that’s with their wall warts not in the circuit.

Here is where I get lost and these are the questions I’m struggling with:

  1. What circuits to I need to introduce to safely keep the batteries charged while at the same time powering the 2.4 amp hour load.

  2. What’s the best battery option to use in this scenario that will keep this rig running for up to 48 hours when the 110 drops out?

  3. If for some reason the blackout lasts longer then the batteries can bare how can I disconnect the load at a preset voltage to keep from damaging the batteries and the equipment?

I don’t want to go with a traditional 110AC UPS because from I can tell they just can’t do the amount of time we need and obviously there is a huge loss when converting from battery to 110AC.

Any advice would be greatly appreciated…